Moisture associated with a tropical wave combined with strong daytime heating and good upper level dynamics, to produce numerous showers with strong thunderstorms which led to very heavy rain across some area of Puerto Rico, mainly in Bayamon, Toa Alta, and Toa Baja.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SJU wrote it up.
Moisture associated with a tropical wave combined with strong daytime heating and good upper level dynamics, to produce numerous showers with strong thunderstorms which led to very heavy rain across some area of Puerto Rico, mainly in Bayamon, Toa Alta, and Toa Baja.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Juan, PR wrote its last area forecast discussion before the first event at Aug 23, 11:54 AM AST, 2 hours 6 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE SAN JUAN PR 1154 AM AST MON AUG 23 2010 .UPDATE...EXPECT A MIXTURE OF SUNSHINE AND CLOUDINESS ACROSS THE LOCAL ISLANDS THIS AFTERNOON...AS A WEAK TROPICAL WAVE AND ITS ASSOCIATED MOISTURE MOVE ACROSS THE LOCAL AREA. THIS FEATURE AND MOISTURE WILL COMBINE WITH LOCAL EFFECTS THIS AFTERNOON...TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS...MAINLY OVER THE CENTRAL AND WESTERN INTERIOR AND WEST SECTIONS OF PUERTO RICO. INHERITED SHORT TERM GRIDS AND ZFP HAD A GOOD HANDLE ON EXPECTED CONDITIONS FOR THIS AFTERNOON AND DID NOT SEND A ZFP UPDATE. FOR THE COASTAL WATERS...MADE A COUPLE OF MINOR ALTERATIONS TO THE PREVIOUS CWF...MAINLY TO THE SYNOPSIS...OTHERWISE NO CHANGES. && .AVIATION...EXPECT PREVAILING VFR CONDITIONS ACROSS THE LOCAL ISLANDS AND AT ALL LOCAL TAF SITES THROUGH TONIGHT. HOWEVER... BRIEF MVFR CONDITIONS AND LOCAL MOUNTAIN OBSCURATIONS ARE POSSIBLE OVER THE CENTRAL AND WESTERN INTERIOR AND WEST SECTIONS OF PUERTO RICO...INCLUDING NEAR OR OVER TJMZ...IN SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS. && .PREV DISCUSSION... /ISSUED 536 AM AST MON AUG 23 2010/ SYNOPSIS...AT UPPER LEVELS...LOW PRESSURE NOSES INTO THE HIGH PRESSURE NORTH OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS AND RETREATS NORTH AS HIGH PRESSURE RETURNS FROM THE EAST OVER THE WEEKEND. WINDS REMAIN LESS THAN 20 KNOTS IN THE LOCAL AREA. AT MID LEVELS...HIGH PRESSURE THAT STRETCHES ACROSS THE ATLANTIC NEAR 27 WEST IS DIVIDED BETWEEN 50 AND 60 WEST BY AN INTRUDING TROPICAL CYCLONE THURSDAY THROUGH SATURDAY. MID LEVELS ARE SOMEWHAT DRY DURING THE NEXT 7 DAYS. AT LOWER LEVELS...A TROPICAL WAVE MOVES THROUGH THE AREA TODAY. A BAND OF MOISTURE MOVES IN ON WEDNESDAY PROPELLED BY HIGH PRESSURE DEFORMING AROUND TROPICAL CYCLONE DANIELLE...WHICH WILL PASS WELL NORTHEAST OF THE AREA. A SECOND WAVE PASSES MAINLY SOUTHWEST OF THE AREA ON SATURDAY. DISCUSSION...A TROUGH BROUGHT CONSIDERABLE MOISTURE AND MODEST RAINFALL AMOUNTS TO THE LOCAL AREA ON SUNDAY AND THE NARROWING DRY SLOT BETWEEN THE MOISTURE IN THE TROUGH AND THE NEXT TROPICAL WAVE NOW APPEARS JUST EAST OF THE U.S. VIRGIN ISLANDS. AT THE PRESENT RATE OF MOVEMENT IT SHOULD PASS THROUGH SAN JUAN DURING THE MORNING FOLLOWED BY AN INCREASE OF MOISTURE THAT WILL TRIGGER MORE SHOWERS AND THUNDERSTORMS OVER THE ENTIRE AREA BEFORE THE DAY IS OVER. THE MOISTURE ACCOMPANYING THE TROPICAL WAVE APPEARS TO BE ABOUT 6 DEGREES OF LATITUDE WIDE TO OUR EAST AND WILL PASS IN ABOUT 24 HOURS. AN ARC OF MOISTURE IS TRAILING THE WAVE BUT NOW APPEARS TO BE SINKING SOUTH AND WILL LIKELY PASS SOUTH OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS ON WEDNESDAY. MOISTURE MAY FILL IN BEHIND THIS WAVE AS WITH THE PREVIOUS ONE AND WITH THE WIND SHIFTING TO THE NORTHEAST SHOWERS IN THE MORNING SHOULD BECOME MORE COMMON ON WEDNESDAY MORNING ALONG THE NORTHEAST COAST AND SHOWERS AND THUNDERSTORMS WILL INTENSIFY IN THE SOUTHWEST IN THE AFTERNOON. WEAK BANDS OF MOISTURE PASS THROUGH THE AREA THURSDAY THROUGH EARLY NEXT WEEK...BUT THE BEST MOISTURE PASSES THE AREA BY ON SATURDAY ACCORDING TO THE GFS AND THE ECMWF. TROPICAL STORM DANIELLE IS STILL STRENGTHENING AND WAS PLACED AT 14.8 NORTH 37.1 WEST AT 5 AM...MOVING WEST NORTHWEST AT 14 MPH. IT IS EXPECTED TO BECOME A HURRICANE IN THE NEXT 24 HOURS AND PASS NORTHEAST OF THE AREA BY MORE THAN 900 MILES ON FRIDAY. AS IT APPROACHES ON WEDNESDAY LOW LEVEL WINDS WILL SHIFT MORE TO THE NORTHEAST...RETURNING TO THE SOUTHEAST ON FRIDAY. THIS SHOULD COOL HIGH TEMPERATURES WEDNESDAY AND THURSDAY FROM TUESDAYS LEVELS...ESPECIALLY ON THE NORTHEAST COAST...BUT WE MAY SEE AN INCREASE ON FRIDAY AND OVER THE WEEKEND. HIGHS IN SAN JUAN WILL BE MOSTLY IN THE LOWER 90S THEN. AVIATION... A TROPICAL WAVE WILL MOVE ACROSS THE LOCAL REGION TODAY INCREASING THE CLOUDINESS AND THE SHRA/TSRA ACTIVITY...ESPECIALLY AFTER 23/12Z. BRIEF MVFR CONDS ARE POSSIBLE IN PASSING SHOWERS ACROSS MOST OF THE TAF SITES. TSTMS SHOULD DEVELOP ACROSS TJMZ AND VICINITY FROM 23/17-21Z...RESULTING IN TEMPO MVFR OR EVEN IFR CONDS. MOUNTAIN OBSCURATIONS WILL OCCUR OVER INTERIOR SECTIONS OF PR. LLVL WINDS WILL BE MAINLY FROM THE EAST NORTHEAST AT 10 TO 20 KTS...WITH HIGHER GUSTS NEAR TSTMS. MARINE...SEAS WILL GENERALLY REMAIN BELOW ADVISORY CONDITIONS TODAY...INCREASE SOMEWHAT DURING THE WEEK AND REACH SMALL CRAFT ADVISORY LEVELS...FROM SWELL FROM TROPICAL CYCLONE DANIELLE ON FRIDAY. SAID SWELL WILL AFFECT THE ATLANTIC WATERS THE MOST DUE TO FETCH AND STRENGTH CONSIDERATIONS. && .PRELIMINARY POINT TEMPS/POPS... SJU 90 80 92 80 / 30 30 40 50 STT 90 81 92 83 / 30 40 40 30 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. &&
HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS NATIONAL WEATHER SERVICE SAN JUAN PR 621 AM AST MON AUG 23 2010 AMZ710>745-PRZ001>013-241030- SAN JUAN AND VICINITY-NORTHEAST-SOUTHEAST-EASTERN INTERIOR- NORTH CENTRAL-CENTRAL INTERIOR-PONCE AND VICINITY-NORTHWEST- WESTERN INTERIOR-MAYAGUEZ AND VICINITY-SOUTHWEST-CULEBRA-VIEQUES- THE NEARSHORE AND OFF SHORE ATLANTIC AND CARIBBEAN COASTAL WATERS- 621 AM AST MON AUG 23 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT A TROPICAL WAVE WILL MOVE ACROSS THE LOCAL AREA TODAY. THIS WAVE AND ITS ASSOCIATED MOISTURE WILL PRODUCE SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. PERIODS OF HEAVY RAINFALL...LOCALLY GUSTY WINDS AND SOME URBAN AND SMALL STREAM FLOODING ARE EXPECTED AS THIS TROPICAL WAVE PASSES BY. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. AMZ715-725-VIZ001-002-241030- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 621 AM AST MON AUG 23 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT A TROPICAL WAVE WILL MOVE ACROSS THE LOCAL AREA TODAY. THIS WAVE AND ITS ASSOCIATED MOISTURE WILL PRODUCE SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. PERIODS OF HEAVY RAINFALL...LOCALLY GUSTY WINDS AND SOME URBAN AND GUT FLOODING ARE EXPECTED AS THIS TROPICAL WAVE PASSES BY. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED.
The San Juan radar (TJUA), 28 km away, was scanning. The volume nearest the first event began at 17:59 UTC.
3 flash flood. Local standard time, as filed.
Several houses were flooded at Country Estates sector in Bayamon.
Cafeteria El Puentecito was reported flooded at Urb . Sierra Linda, Road 14 in Bayamon.
A house was reported flooded at Urb. Magnolia Garden in Bayamon.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2010Every state in 2010This day in weather historyWarnings in Puerto Rico, August 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 256801, 258029, 258030.